In cases of spinal injury, surgery to remove an intervertebral disc in the spinal column may be necessary. The vertebrae of the spinal column are connected together by intervertebral fibrocartilaginous discs. The discs maintain a separation between the vertebrae, but are sometimes damaged and/or become narrowed so that the intervertebral separation is reduced. This produces pain, and in order to alleviate the symptoms resulting from this intervertebral disc failure, a disc may need to be removed.
When a disc has been removed, the vertebrae may be fused together, resulting in complete loss of flexibility of the spinal column at this location, or the damaged disc may be replaced with a disc prosthesis intended to duplicate the function of the natural spinal disc. Many such spinal disc prostheses have been proposed, but none are completely satisfactory.
The patent to Kuntz, U.S. Pat. No. 4,349,921 describes an intervertebral disc prosthesis comprising a body of biologically-acceptable material suitably dimensioned and shaped to replace a natural disc. One end of the prosthesis has a raised flange to prevent penetration of the disc prosthesis to an excessive depth into the spinal joint. The prosthesis is made up of several laminar sections, placed vertically. This device, having its parts located in side-by-side relationship does not give the spine sufficient flexibility. The patent to Froning, U.S. Pat. No. 3,875,595, shows a collapsible plastic bladder-like prosthesis, for filling with liquid. The top and bottom surfaces of the synthetic disc have stud-like protrusions which fit into sockets fastened into the adjacent vertebrae. The device is complex, and requires physical attachment to the adjacent vertebrae.
The patent to Stubstad, U.S. Pat. No. 3,867,728, shows a shaped spinal prosthesis having a top covering and a bottom covering which are secured together using textile fabric. The Patil patent, U.S. Pat. No. 4,309,777 describes an artificial intervertebral disc for implantation in the disc space after removal of a damaged disc. The Patil disc has a plurality of springs positioned between top and bottom surfaces to provide flexible movement of the vertebrae. The intervertebral disc of Patil is secured with a plurality of spikes extending upward and downward from the prosthesis, anchoring the disc to the vertebrae.